Calvinman

Hi hsukaria, I have had a look through the needle valve and the fuel nipple and all looks good, I only wish I could find some sort of restriction. The O ring at the base of the carb seems to be in good shape and seems to be seated properly and the O rings on the needle valve look find. Hopefully I will fire it up, get it up to full speed, set the needle and all will be good.

hsukaria

Yeah, Calvinman is from Manitoba. That is too cold even for me, from Michigan. I ran a couple of 4-strokes (Saitos) in the cold last winter and I didn't even have to adjust the needles from summer. I was impressed.

As far as nickel plating on tuned pipes, I have an OS 61FX on a quiet pipe. I have purchased a set of ASP piston/liner hoping that it fits if the nickel ever peels. But as we all know, only OS piston/liners fit on the AX series unfortunately. So I traded the OS 55AX away as a parts engine.

aspeed

I was just thinking about Manitoba, maybe a bit more nitro because it is so cold? I found it runs better. Maybe a cover over the cylinder to block the fins. It could also be varnished up which will prevent full throttle, and of course air leaks. Some of the combat guys using the ASP motors with carb problems put a little dab of silicone caulk on each little nut that screws into the carb housing, and the carb hold down screw... every possible spot imaginable. For the varnish, a Scotchbrite pad dipped in acetone or laquer thinner to scrub the liner works well, and the piston too if you want to take it out.

hsukaria

I think Calvinman said he has a heated area to run his engine. Pretty nice to have in Manitoba. How long is the summer season there, 3 weeks?

Calvinman

Ha ha, it sure seems like it hsukaria, too much time to build and not enough time to fly. I was looking at the engine tonight and also an older OS46 I reringed that I want to run up a bit. The MDS has a shim in it already so I may indeed be able to run higher nitro, but I have a gallon of 5% to try it with. Everything looked good as far as possible air leaks with the exception of the rear cover O-ring my be slightly inside of the top where the port comes close to the back of the engine so I put a little RTV on the back plate. I'm going to wait until tomorrow to run them so the RTV has lots of time to set up.

1QwkSport2.5r

Just because it has a head shim doesn't necessarily mean it's setup for higher nitro. Youll know the nitro is too high when you set your needle for flight and hear a crackling sound at WOT. Random flame outs will happen too sometimes.

Calvinman

Ok, I ran up the OS and it seems to be running well, I can't tach it under the artificial light though and I have the fusalage wired down to a table so I cant heft it nose up to feel the pull. Next I ran the MDS with 10% and an 11x6 APC, it went to full thottle very rich and when I leaned it up it would surge from rich to lean, then die. I took some video now I have to figure out how to post it. I am going to run it with a 11 x5 prob made for a nexstar or something like that.

Calvinman

Ran it up with the 11x5 and at first it wouldnt run right. I leaned up the bottom end 3/4 of a turn, I had it at 2 and 1/2 and I think raw fuel was going through the crank in waves causing the surging? It revved up and ran really strong for about a minute then quite. I'm going to try some 5% (MORE LIKE 7% because I'm adding the 5% to 1/4 gallon of 10%)

Calvinman

I have the low end down to 5/8 of a turn less a screwdriver blades thickness worth. It now seems to run well, but when going to full throttle it takes a few seconds for it to get up to full revs. I wish I could put a tach on it. I'm going to try the 11 x 6 again as it almost sounds like it may be revving a little high with the 11x 5 on it.

Calvinman

With the 11 x 6 the engine quite after a few seconds at full throttle with the same needle setting(High end) and I leaned it an eights or a quarter to keep it running. The motor seemed to be lugging though, maybe a 10 x 6 or the 11 x 5 is a better choice. I am going to run it a bit more on Sunday. I am going to double check the balance on the 11 x 5 because one of the head bolts vibrated clean out, I was lucky to spot it on the floor.

Calvi

Hobbsy

My Feedback: (102)

The MDS .48 is a great engine, an 11x6 will not lug it, MDS' get accused of having lousy carbs. The fact is that the LS needle has a short, almost blunt, taper, therefore the sweet spot is narrow. Tune slowly. Plug wise, use a Fox Miracle, H9 or an OS-f.

aspeed

You can get a tach reading by using a flashlight on the other side of the prop. I do that when I get a late start, and it works better than the sunlight even. If it is sputtering when giving full throttle, it is rich, if it cuts out fairly quickly it is lean, although it could recover from the lean and seem rich.(just to add some confusion)

jaka

Hi!
11x5 prop is a bit too small for most models if you fly at sea level! A 11x6 or 12x4 prop is much better.
When you run the engine at full throttle and then adjust the high speed needle a little so the rpm goes down some and then throttle down...what happens then? Does it idle ok at around 2500-3000rpm ?

Calvinman

Thanks for the replies guys, For tonight I am going to give an APC12 x 4 a try. If I can make it to the hobby shop tomorrow I will pick up a fox miracle plug, and maybe an OS-f

Calvi

hsukaria

Just for kicks if you haven't done it yet, check that the muffler pressure nipple is not clogged.

Also, when the engine is running, wiggle the high speed needle side to side to see if it is loose and causes mixture change.

the pope

How hot is the engine getting when it quits ? If the head bolts are backing out that could be a sign that its getting too hot . Have u checked for a warped head ! I had like Husky mentioned a blocked muffler nipple on a Supertigre 34 and it ran for a bit and then stopped .I dont think it went as long as a minute though .

1QwkSport2.5r

I think getting the right fuel in the fuel tank would help. Get some 0-5% nitro fuel in the tank and run it. Start from a rich setting on both needles. Set the high end 500rpm rich from peak and leave run for 10-20 seconds. Drop down and set the idle/transition.

I highly doubt a 4-stroke glow plug is going to do you much good.

Calvinman

I hope the head is not warped, I think the 11-4 which I balanced on my magnetic balancer and is the one prop that I never rebalanced when I replaced it with a jeweled movement balancer just litteraly just shook it out with the high revs.

There is a tiny bit of side to side play on the needle valve , the O ring still looks ok and it takes a push to get it into the barrel. I replaced the 1 mm long chunk of fuel tubing that is between the knob and the threads with one about 3 mm long and it has stabilized the needle valve. It seems like I am going in the right direction, I hope I can get this motor running well enough to use in my fleet, when it does run well it sure makes some nice power.

Calvi

Calvinman

Oh, and it sure is sweet to have the smell of some nitro and castor in my nose after a long cold winter

hsukaria

By the way, at what elevation are you? I don't know if it has been asked already.

Calvinman

not much we are at 600 feet here in Winnipeg

Calvinman

I ran it with the 12 x 4 and it revved out and almost quit, had to back off the throttle and lean it a tad, got it running really nice. The needle valve does not seem to be very sensitive with about a half turn back from peak to make the revs drop.

I let it idle for 30 seconds and it accelerated niclely to full throttle. I then let it idle for about a minute and it started it's surging at full throttle and died, I leaned up the low end a half a screwdriver blades thickness and I am waiting for it to cool down to retry it. I will see if I can get a decent temperature reading with the infra red when I run it again.

Calvinman

The engine revs like crazy, I tried using my tach with a flashlight but I was only getting 8,000 rpm out of it and I really don't believe that.

When I first start it I usually prime the carb with 2 or 3 drops of fuel and for some reason that seems enough to snuff the engine when I go to full throttle unless I take about 30 seconds to get there. Once the prime has been blown out I can accelerate rapidly with no stumbling or flame out unless I let it idle for over a minute. It seems like the low end needle might be closed but may see if it has some more left in it tomorrow.

I would like to try a shim also and may slip down to the hobby shop to see if they have one to fit.

1QwkSport2.5r

Any quitting or flaming out at WOT tells me it's set too lean. I would always start rich and work lean. Even high strung engines that don't like much nitro should run without quitting when set rich. Work leaner until the rpm says a little, then open the needle back up 1/4-1/3 turn or so. After a few seconds, pinch the fuel line close to the carb momentarily. If the rpm drops, it's too lean. No change in rpm means it's peaked, and a rise in rpm means it's rich. You want a slight rise in rpm.

aspeed

Sounds like a lean low speed needle to me.